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1

This appeal is from the decision of the board which affirmed the examiner's rejection of claims 1 through 5 and 9 in appellants' application1 for "Production of Micro-Sized Metal Particulates."

2

Appellants' application involves a process of converting metal to a finely divided form. The metal in its original form is utilized as the anode of a "high erosion arc," termed a "hierarc." When a sufficiently high current density is established between the metal anode and a cathode material, a "hierarc" forms, vaporizing the metal anode, and the vapor is projected from the anode as a high speed ionized jet (tail flame) several feet in length. As the material in the tail flame loses its energy by radiation, the ionized vapor rapidly cools and condenses to form minute, discrete particles, called "fume," which are subsequently collected. The arc may be established in an inert atmosphere or vacuum to assist cooling of the vapor in the tail flame. The process is reflected in claim 4:

3

"4. The process of converting metals to fume form which comprises maintaining a high erosion arc with such materials as anode and with a cathode in an inert atmosphere and cooling the resultant vapors and separating out the resultant fume."

Sheer et al. disclose a process for producing a refractory material, such as silica, in finely divided form by vaporizing an anode of the material, utilizing a high erosion arc. The vaporized material is emitted from that electrode in the form of a high velocity tail flame. The vapor is quickly cooled and condenses, forming finely divided particles of silica fume. Sheer et al. describe the high erosion arc as "an entirely different electrical phenomena from the common arc." It is described as coming into being as a sudden transition from the common arc when current densities at the anode face are employed which exceed a critical value. The higher current density results in a higher temperature at a part of the anode known as the crater, yielding a sharp increase in the rate of erosion or vaporization of the electrode. The temperature of the common arc is said to be insufficient "to cause more than a negligible vaporization of the anode."

6

Torikai discloses a method of manufacturing fine powders of various metals or metal oxides. Two metallic electrodes are placed in a chamber in which air or an inert gas is maintained at sub-atmospheric pressures. The striking of an arc between the electrodes results in formation of finely divided powder which settles in the electrode chamber or may be collected in a second condensing chamber. As stated by Torikai, "It is well known that when electric discharge takes place between electrical conductors the molecules of electrode material become disintegrated owing to ionization and serve as a current carrier." Further on, Torikai says "The particles vaporised from the electrodes then produce a powder * * *."

7

The examiner rejected claims 1-5 and 9 as unpatentable over Torikai in view of Sheer et al. He recognized that Torikai does not disclose the use of a "high erosion arc," but instead apparently uses a common arc to form the finely divided metal powder. Nevertheless, he was of the opinion that it would be obvious to one of ordinary skill in the art to utilize the high erosion arc of Sheer et al. in place of the specific arc used by Torikai, particularly since Sheer et al. make it clear that a high erosion arc results in a much higher temperature and a concomitant faster electrode vaporization. The board agreed.

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8

In our analysis of the record in light of appellants' contentions, we find nothing which demonstrates that the examiner and board erred in rejecting the claims. We subscribe to the view that the worker in this art would have no difficulty in recognizing the efficacy of using the high erosion arc of Sheer et al. in the process of Torikai. Appellants' arguments concerning the importance of "shock chilling" the ionized vapor immediately upon formation to produce 0 ultra fine powder of 30 to 200 A2 size are irrelevant since the disclosure and the appealed claims fail to allude to that technique or result. We are persuaded that the differences between the subject matter sought to be patented and the prior art are such that the subject matter as a whole would have been obvious to one of ordinary skill in this particular field.